When RelayRides, a "peer-to-peer" car-sharing marketplace, started in San Francisco last year, Caterina Rindi was the first person to sign up.
She rents out her Prius for $7 an hour.
"I make about $200 to $250 a month," she told ABC News.
It's enough to cover her insurance and car expenses.
The service, currently available only in San Francisco and Boston, is similar to the popular Zipcar, except that RelayRides rents out people's personal cars.
Now, thanks to a new, exclusive deal with General Motors, RelayRides is hoping to connect more car owners looking to make extra money with those in need of a temporary ride -- and watch its business really take off across the country.
GM announced today that it was partnering with the company and allowing millions of its vehicle owners to use the OnStar system to rent out their idle cars.
RelayRides, which started last year, currently has about 200 cars and 3,000 users enrolled in San Francisco and Boston, said Shelby Clark, founder of RelayRides.
"So far, the average car owner has made about $250 a month in their pocket, but we've seen those numbers go up to $600 to $1,000 a month," Clark said.
RelayRides provides an online site where car owners can choose to rent out their vehicles. The owners control the rates and availability and the company offers a $1 million insurance policy to secure the transaction.
The OnStar service will allow borrowers to unlock GM cars with their mobile phones -- eliminating the need for extra keys or equipment. RelayRides will install a small device inside vehicles without OnStar to provide access to renters.
With a mobile application, the OnStar technology will also let RelayRides customers search for available cars, reserve them online and locate them using a global positioning service.
"We're using technology to make both our older and newest models car-share ready and available for those owners who choose to participate in car-sharing," Stephen Girsky, GM's vice chairman, said in a news release on the automaker's website.
The partnership between GM and RelayRides will roll out next year in Northern California.
Here are other personal car-sharing sites: